You're likely to see this name right at the top of any comprehensive catalog of dinosaurs. The problem is that it not only wasn't a dinosaur, it wasn't even an animal.

Aachenosaurus multidens was named after the place of its discovery, the Aachenian deposits of Moresnet in Belgium. In 1887, Abbey G. Smets, professor of natural sciences at a nearby college, discovered what he believed to be two pieces of jawbone from a new type of hadrosaur, a herbivorous bipedal dinosaur standing 4 to 5 meters high. He proceeded to give a detailed description of the animal, claiming to have examined the "bones" under a microscope as well.

Smets presented his findings to the Belgian geological society in 1888. A Mr. Dollo visually examined the specimens and determined them to be petrified wood.